Very unlikely. It's up to Nintendo, but I imagine it would require a pretty significant re-write in order to make the Wii U gamepad's input mimic that of a Wiimote w/extensions, as well as possibly a way to switch between them... Basically, vWii mode is done, and it doesn't seem very likely that Nintendo will be messing with it much (if at all) in the future.
Much of the Wii U-exclusive hardware is also disabled during vWii mode, so they would have to leave that code enabled in order for the gamepad to allow button input. This basically defeats the purpose of doing vWii mode the way they did where it is essentially a Wii within the Wii U. If they had any plans to allow playing Wii games with the Wii U gamepad, they would have planned things out completely differently.
Basically your only hope is the off-chance that they do allow the gamepad to be used as a classic controller. (Because it simply would NOT make sense as a Wiimote by itself, nor as a nunchuck.) But again, this would have some weird compatibility/security issues for them to sort through, and it wouldn't really be a beneficial business decision on Nintendo's part.